1. Field to which the Invention
The present invention relates to position detecting apparatus with DSRC feature and its control method, and in particular to a driving-support system in automobile applications.
2. Description of the Related Art
Conventional position detecting means using radio waves include a position detecting system using satellites and a position detecting system using communication base stations.
The former is a position detecting system using a scheme whereby radio waves are received from a plurality of satellites on a predetermined orbit and the current position of the user is obtained from the difference of the time required for radio waves to reach the Earth. Standalone technologies include the GPS (Global Positioning System) and the GLONASS (Global Navigation Satellite System).
The latter is a system whereby the approximate position of the user can be detected at the center of a telecommunications operator by determining which base station area the user is located through the use of densely installed communications base stations. The PHS (Personal Handyphone System) is one of such technologies currently in use.
In addition to the position detecting systems that use satellites, the DSRC (Dedicated Short Range Communication) technology is drawing people""s attention and used for communication means etc., in the ETC (Electronic Toll Collection system) apparatus.
When wishing to mount a position detecting system using satellites and a DSRC system on car navigation apparatus, etc. at the same time, high costs and increased power consumption are major problems that prevent such an implementation.
In conventional car navigation apparatus, as shown in an example of FIG. 11, a GPS module 601 is mounted as position detecting means and a DSRC module 602 for ETC is mounted as a DSRC system, both interconnected with a navigation apparatus main unit 603 for displaying information to the driver. The GPS module is composed of an antenna section 604 for receiving GPS signals, an RF section 605, and a GPS baseband processor 606. The GPS baseband processor 606 uses a GPS signal preprocessor 608 for performing high-speed demodulation on RF input signals 607 that have been converted to the baseband bandwidth and uses a CPU 609, a ROM 610, a RAM 611, an RTC (real-time clock) 612, and a non-volatile RAM 613 dedicated for GPS for controlling the GPS signal preprocessor and process and save demodulated signals.
Meanwhile, the DSRC module 602 is composed of an antenna section 614 for receiving DSRC signals, an RF section 615, and a DSRC baseband processor 616. The DSRC baseband processor uses a DSRC signal preprocessor 618 for performing high-speed demodulation on RF input signals 617 that have been converted to the baseband bandwidth and uses a CPU 619, a ROM 620, a RAM 621, a cipher processing circuit 622, and a memory card 623 dedicated for DSRC for controlling the GPS signal preprocessor and process and save demodulated signals.
Power supply used is adapted, as shown in FIG. 12, to directly feed power to the GPS module 701 and the DSRC module 702.
DSRC map data supply mechanism, as shown in FIG. 13, is composed of a geographical information DB (database) 803 that provides ROM geographical information 802 recorded on CD-ROMs, etc., depending on the search input 801, position detecting apparatus 805 for outputting the current coordinate information 804, a display data generation circuit 807 for inputting coordinate information and searching the geographical information DB to acquire RAM geographical information and to generate and output geographical display data 806 corresponding to the geographical display range on the monitor, and a monitor 808 for receiving and displaying the geographical display data.
Geographical data display operation using position detecting apparatus and with DSRC apparatus is executed according to the flowchart in FIG. 14.
First, after display operation has started, in step S901, coordinate information is acquired from the GPS. Instep S902, display range is determined according to the coordinate information. In step S903, collation with the geographical information DB is made to determine whether a tollgate is present or not in the display range, and if any, in step S904, the tollgate coordinates and the toll are overlapped on the geographical image to generate display data. Otherwise, in step S905, the geographical image alone is displayed on the monitor as display data.
Next, activation of the DSRC section will be explained with reference to the flowchart in FIG. 15.
Once the DSRC section is activated via starting the engine of a vehicle, the DSRC section is under permanent power feed. In step S1002, the carrier sense, or output to detect whether radio waves in a bandwidth to be received are present or not, is checked. In case no carriers are detected, execution is exited and DSRC baseband processing is terminated. Otherwise, DSRC signal processing is executed in step S1004.
However, providing separate communication circuits in the position detecting means and the DSRC means has a drawback that product costs and power consumption are too high.
The invention is proposed in view of the foregoing situation and aims at reducing power consumption and providing low-cost and compact position detecting apparatus with DSRC feature and its control method.
Position detecting apparatus with DSRC feature according to the first aspect of the invention comprises position detecting means for receiving radio waves for position detection and outputting position information and DSRC means for receiving radio waves for DSRC and processing signals, characterized in that the position detecting means and the DSRC means are controlled via the same CPU and share part or whole of storage means and that the position detecting means is adapted to operate in either the full drive mode or suppress mode.
Via such a configuration, the position detecting means is adapted to operate at least in the full drive mode and suppress mode so that both modes can be used without increasing the throughput of CPU, by normally driving the position detecting means in the full drive mode and using the suppress mode only when the DSRC means is used.
Position detecting apparatus with DSRC feature of the first aspect of the invention according to the second aspect of the invention is characterized in comprising timing signal generating means for determining the approach to a DSRC base station and driving the DSRC means as well as placing the position detecting means in the suppress mode.
Via such a configuration, in addition to the advantage of the first aspect of the invention, the approach to a DSRC base station position is determined, timing signals are generated, and the timing signals are used to place the position detecting means in the suppress mode. This allows position detection and DSRC to be performed more efficiently.
Position detecting apparatus with DSRC feature of the first or second aspect of the invention according to the third aspect of the invention is characterized in further comprising a geographical database and position-related information adding means that adds and saves anew onto the storage means information obtained via DSRC means and new DSRC base station position information.
Via such a configuration, in addition to the foregoing advantages, received information that is not found in the database can be easily added. Position-related information can be automatically added within apparatus. This eliminates the need for updating the database thus saving database update costs. The storage means may be separately provided to store DSRC base station position information or the information may be stored in storage means for GPS.
Position detecting apparatus with DSRC feature of the second aspect of the invention according to the fourth aspect of the invention is characterized in that the position detecting means is adapted to enter the suppress mode on the arrival of timing signals from the timing signal generating means and to enter the full drive mode in synchronization with drive halt signals from the DSRC means.
Via such a configuration, in addition to the foregoing advantages, efficient use of power is allowed thus attaining cost reduction.
Position detecting apparatus with DSRC feature of the fourth aspect of the invention according to the fifth aspect of the invention is characterized in that the position detecting means is adapted to store position information before arrival of the timing signals in the storage means in the suppress mode and to read the position information from the storage means in synchronization with the drive halt signals from the DSRC means as well as to correct position information from the position information and correction information that is based on its history in order to use the resulting corrected information as return position information and to enter the full drive mode.
Via such a configuration, during DSRC, position information is corrected from the correction information and the correction information that is based on its history and the resulting corrected information is output as return position information, rather than suppressing driving of the position detecting means. Thus, position information can be displayed during communications with a DSRC base station without excessively intervening with position detecting operation. For example, using the output information as an initial value for the approximation in the GPS positioning calculation reduces the amount of operation. For the PHS, the output information may be used without approximation.
Position detecting apparatus with DSRC feature of the first aspect of the invention according to the sixth aspect of the invention is characterized in that, in the suppress mode, the DSRC means is driven with top priority and that operation of the position detecting means is suppressed in order not to give effects to the DSRC means.
Via such a configuration, suppressing the position detecting feature to prevent out of tracking makes it unnecessary to follow a step for returning from out of tracking in returning operation, thus suppressing the delay time in restarting positioning.
Position detecting apparatus with DSRC feature of the first aspect of the invention according to the seventh aspect of the invention is characterized in that, in the suppress mode, the position detecting means is turned off.
Via such a configuration, a lower-throughput CPU can be used and power reduction is possible that accompanies halting of operation of position detecting means.
Position detecting apparatus with DSRC feature of the first aspect of the invention according to the eighth aspect of the invention is characterized in that the position detecting means is adapted to be mounted on a vehicle, to detect and display the running position of the vehicle and that the DSRC means is an ETC (Electronic Toll Collection) system.
Via such a configuration, toll payment apparatus on a freeway or in a parking lot can be implemented with the minimum costs and power consumption.
A control method for position detecting apparatus with DSRC feature according to the ninth aspect of the invention comprises a position detecting step for outputting position information by receiving radio waves for position detection and a DSRC step for communicating with a DSRC base station, characterized in that the position detecting step is adapted to enter the suppress mode during the DSRC step.
Via such a configuration, the position detecting means normally performs position detection in the full drive mode and performs position detection in the suppress mode only when the DSRC means is used so that both modes can be used without increasing the throughput of CPU. This attains considerable reduction of power consumption.
While detecting xe2x80x9cposition informationxe2x80x9d via position detecting means refers to detecting the position where radio waves were received, it is assumed that it also refers to detecting general. xe2x80x9cpositioning informationxe2x80x9d such as time and correction information related to calculation as well as position information. Positioning information comprises position information including history of position obtained from time difference of signals coming from satellites and is so-called position-related information including a plurality of pieces of information that causes position, time, and calculation to converge in an early stage.